Other non-specific observations such as a chronic cough, unilateral wheezing, haemoptysis or pulmonary infections can also contribute to long delays (a mean of 20 months according to Gaissert and Mark) before a correct diagnosis is made.

Exploratory methods vary in efficacy but may also be complementary.

Radiology

The chest X-rays may be normal, show a solitary nodule or a bronchial obstruction with downstream atelectasis.

The CT scans can reveal a well-defined intraluminal mass, typically with an air meniscus sign, suggesting the endobronchial and expansive nature of the tumour.

Endoscopy

Bronchoscopy will find a firm, smooth, shiny and well-defined intraluminal mass that is sometimes pedunculated.

On average, the mass will have a diameter of ∼18 mm (8–68 mm in the series reported by England et al.).

Endoscopic specimens are generally insufficient for confident diagnosis; complete resection is recommended as this allows for thorough histological analyses and is usually curative.

Endoscopic removal has been described, but total surgical resection remains the reference.

Microscopy

Histology studies will find a well-circumscribed (but unencapsulated) proliferation of mucosal glands in the form of an exophytic nodule with no invasion of the cartilage or bronchial wall.

The lesion is composed of variously dilated, sometimes cystic glands filled with mucous.

Tubules and papillae may also be present.

Glands in the tumour are lined with mucous-secreting cells whose form may be columnar, cuboidal or flattened.